Environmental Engineering Reference
In-Depth Information
The influence of the feed flow rate on the production of the distiller is shown on figure 9,
where the total distillation flow rate decreases when the feed flow rate increases: respectively
from 1.4 to 0.5 kg/m 2 .h for the production and from 3 to 20 kg/m 2 .h for the feed flow rate .
The variation of the distillate of a multi-stage distiller with respect to the different
operating parameters is in agreement with the variation of the production for a single cell. The
obtained results show that the production of a multi-stage distiller can reach 1.5 kg/m 2 .h,
corresponding to a daily production of about 12 kg/m 2 . This result is well above that a
classical distiller the daily production of which varies between 4 and 6 kg/m 2 in the same
conditions.
Conclusion
Several phenomena playing opposite roles in energy balances intervene during distillation
of salted water in a cavity. Their complexity and their competition make the use of
experimental studies necessary in order to better approach the couplings and antagonisms and
their influence on the distillation yield. The present study has been performed in this way and
examines experimentally the energy aspect and the analysis of the contribution of the
different types of heat flux densities occurring in the process of salted water distillation in a
cavity.
It has been shown that when the feed flow rate is low, the latent heat flux density
associated to the change of phase overcomes the other occurring heat flux densities, in
agreement with the conclusion of several authors [3, 6, 11, 21, 22, 23, 24]. The distillation
yield can be improved by increasing the temperature of the feed water. It is explained by the
income of energy that results as a preheating of the cell.
The study of the feed flow rate has shown a great sensitivity of the yield of the cell to this
parameter. The production of pure water drops by a factor equal to two when the feed flow
rate increases from 1 à 5 l/h. This decrease is explained by the increase of the sensitive heat
flux density evacuated by the brine.
From the results obtained in the case of a single cell, the production of a three-stage solar
distiller could be determined. Thus the influence of the different operating parameters on the
distillate flow rate was studied and shown to be in agreement with the results from a single
cell. The final results conform to those of Bouchekima [27] who followed the behavior of a
three-stage distiller on a real site, in South Algeria.
The production of a three-stage distiller can reach in some conditions 12 kg/m 2 per day,
which represents a noticeable improvement with respect to a classical distiller the daily
production of which remains comprised between 4 and 6 kg/m 2 .
Finally, this experimental study has shown that the thermal yield of the distillation cell
remains limited and always below 0.6. The increase of the yield of solar distillation can be
performed by using systems where a separation between the compartment of evaporation and
the compartment of condensation is realized.
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